This invention relates to a method of producing a bending device for use in an endoscope or the like.
Japanese Laid-Open (Kokai) Utility Model Application No. 157302/82 discloses a bending device for use in an endoscope which device is bendable in four directions. This bending device comprises a ring assembly, and four operating wires.
The ring assembly comprises a number of joint rings arranged in a row and pivotally connected to one another. More specifically, each of the joint rings has a pair of first diametrically-opposite connecting portions, and a pair of second diametrically-opposite connecting portions circumferentially spaced 90.degree. from the first connecting portions. The first connecting portions and the second connecting portions extend in opposite directions along the axis of the ring assembly, that is, in the direction of the width of the joint ring. For example, the first connecting portions extend forwardly while the second connecting portions extend rearwardly. A through hole is formed through each of the connecting portions.
The connection between the adjacent joint rings will now be described. The pair of second connecting portions of the forward joint ring are pivotally connected respectively to the pair of first connecting portions of the rearward joint ring by respective rivets passing through the through holes of the connecting portions.
The joint rings are connected together in the following manner. The joint rings are fitted in a row on an elongated support base of a circular cross-section supported in a cantilever manner. The second connecting portions of a forward one of any two adjacent joint rings are superposed respectively on the first connecting portions of the rearward joint ring, and the rivets are passed through the respective mating through holes of these connecting portions. The rivets are deformed by a punch disposed outside the joint rings, thereby pivotally connecting the first and second connecting portions together.
Since the punch is disposed outside the joint rings, the head of each rivet is disposed inside the joint rings, with the distal end of the stem of the rivet projected outwardly from the outer periphery of the joint ring, and in this condition the rivet must be deformed. This invites the following disadvantages. The rivet must be first disposed inside the joint ring, and then the stem of the rivet must be passed through the through holes of the mating connecting portions. Thus, the position of the rivet can not be confirmed with the eyes, and therefore the operability is not good. Particularly when forming the ring assembly of a small diameter, the operability is extremely bad.
In addition, since the support base is of the cantilever type, it has a low strength and can not satisfactorily receive the force applied from the punch. This results in problems that the deformation of the rivet is incomplete and that much time is required for deforming the rivet. These problems are serious particularly when forming the ring assembly of a small diameter.
With respect to other prior art, Japanese Laid-Open Utility Model Application No. 5501/81 discloses a technique in which adjacent joint rings are connected together by stepped rivets. Although each rivet is fixed to an outward one of the mating connecting portions, the rivet is positively angularly movable relative to the inward connecting portions.
Japanese Laid-Open Utility Model Application No. 108027/85 discloses a technique in which a connecting member having a stem is fixed by a laser or the like to an outward one of mating connecting portions of adjacent joint rings.
Japanese Laid-Open Utility Model Application No. 10605/80 discloses a bending device comprising a spring and a plurality of rings for keeping the pitch of the spring constant. Each ring is composed of a pair of arcuate members of a semi-circular shape fixed together at their ends. However, the rings are not connected to one another, but are merely held in contact with one another. Thus, the rings do not constitute a ring assembly.
Japanese Laid-Open Patent Application No. 166137/82 discloses a bending device in which each pair of arcuate members of a semi-circular shape are bent at their opposite ends to form insertion portions, and wires are passed through the insertion portions to thereby connect the pair of arcuate members to form a ring. The adjacent rings are connected together by these wires, so that the rings constitute a ring assembly. This ring assembly is low in strength.